We investigated the association between exposure to environmental risks in early childhood and the prevalence and persistence of conduct difficulties (CD) in children with intellectual disability (ID) who did not have autistic spectrum disorder (ASD), children with ASD and typically developing (TD) children. Results indicated that: (1) exposure to risk was associated with elevated prevalence of CD at age three and, for TD children and children with ID, increased risk of CD persisting to ages five and seven; (2) at all levels of risk, children with ASD were more likely to show persistent CD than other children; (3) children with ID were no more likely to show persistent CD than TD children at low levels of exposure to environmental risk.